1. Field of the Invention
The present invention relates to relates to spinal prostheses and, more particularly, to dimensionally adjustable spinal prostheses.
2. Background Information
Vertebrae and/or discs of a human spine can sometimes be damaged due to disease or injury, may be malformed through a congenital defect or can simply deteriorate due to age. In other cases, vertebrae and/or discs may become fractured, compressed or otherwise damaged. In these and other situations the vertebrae and/or discs can cause an undesired and/or abnormal curvature of the spine with respect to lordosis or kyphosis.
Because of this, orthopedic surgery may be utilized to replace one or more vertebrae or discs with a spinal prosthesis or one or more vertebrae may be repaired via kyphoplasty or vertebroplasty. In the case of disc replacement, the spinal prosthesis may be used between adjacent vertebrae in order to provide proper spacing of the vertebrae. A spinal prosthesis may also be used to promote fusion between adjacent vertebrae. When so utilized, bone or bone fusion material is often placed about or in the spinal prosthesis in order to promote growth of bone between the adjacent vertebrae.
One type of spinal prosthesis may also be used in place of a vertebra or a vertebra and adjacent disc. The vertebra and disc are removed. This type of spinal prosthesis is then placed between remaining adjacent vertebrae as the middle vertebra has been removed. When this is the case, the adjacent discs may also be removed.
When such spinal prostheses are used, it is desirable for them to engage as much surface of the vertebral bone as possible in order to provide support to the bone and to thereby reduce the likelihood of subsidence of the device into the bone resulting from contact pressure of the prosthesis against vertebral bone surfaces. Subsidence can occur since part of the vertebral bone is somewhat spongy in nature, especially near the centers of the adjacent vertebrae.
Because anatomical relationships for each patient are different, it is desirable to have a spinal prosthesis that may be varied in various dimensions. One such aspect is the height or axial (superior/inferior) length of the spinal prosthesis. As such, it is desirable to provide a spinal prosthesis that is dimensionally adjustable in height. Accordingly, there presently exists a need for height adjustable spinal prostheses.